This isn't accurate. Basketball has an age cutoff in pretty much all circumstances I've seen, and usually states that the player can't be older than age X by date Y, while also stating what grade is eligible (along with what exceptions are possible, and what ages are applicable). The complication comes in that these details vary across tournaments and geographies, so what is the effective cutoff in one circumstance can be very different in another. One example is below. The way the dates & ages are aligned, through the 6th grade division, there aren't as many "holdbacks". But once in 7th grade, the age skips a year, and holdbacks are much more common. This appears to address the fact that once in high school, a talented freshman is going to play against varsity seniors who may be 18/19 anyway.
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